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<body>
<p>
Access to date and time using fields and units.
</p>
<p>
This package expands on the base package to provide additional functionality for
more powerful use cases. Support is included for:
</p>
<ul>
    <li>Units of date-time, such as years, months, days and hours</li>
    <li>Fields of date-time, such as month-of-year, day-of-week or hour-of-day</li>
    <li>Date-time adjustment functions</li>
    <li>Different definitions of weeks</li>
</ul>

<h4>Fields and Units</h4>
<p>
Dates and times are expressed in terms of fields and units.
A unit is used to measure an amount of time, such as years, days or minutes.
All units implement {@link org.threeten.bp.temporal.TemporalUnit}.
The set of well known units is defined in {@link org.threeten.bp.temporal.ChronoUnit},
for example, {@link org.threeten.bp.temporal.ChronoUnit#DAYS}.
The unit interface is designed to allow applications to add their own units.
</p>
<p>
A field is used to express part of a larger date-time, such as year, month-of-year or second-of-minute.
All fields implement {@link org.threeten.bp.temporal.TemporalField}.
The set of well known fields are defined in {@link org.threeten.bp.temporal.ChronoField},
for example, {@link org.threeten.bp.temporal.ChronoField#HOUR_OF_DAY}.
An additional fields are defined by {@link org.threeten.bp.temporal.JulianFields}.
The field interface is designed to allow applications to add their own fields.
</p>
<p>
This package provides tools that allow the units and fields of date and time to be accessed
in a general way most suited for frameworks.
{@link org.threeten.bp.temporal.Temporal} provides the abstraction for
date time types that support fields.  Its methods support getting the value
of a field, creating a new date time with the value of a field modified,
and extracting another date time type, typically used to extract the offset or time-zone.
</p>
<p>
One use of fields in application code is to retrieve fields for which there is no convenience method.
For example, getting the day-of-month is common enough that there is a method on {@code LocalDate}
called {@code getDayOfMonth()}. However for more unusual fields it is necessary to use the field.
For example, {@code date.get(ChronoField.ALIGNED_WEEK_OF_MONTH)}.
The fields also provide access to the range of valid values.
</p>

<h4>Adjustment</h4>
<p>
A key part of the date-time problem space is adjusting a date to a new, related value,
such as the "last day of the month", or "next Wednesday".
These are modeled as functions that adjust a base date-time.
The functions implement {@link org.threeten.bp.temporal.TemporalAdjuster} and operate
on {@link org.threeten.bp.temporal.Temporal}.
A set of common functions are provided in {@link org.threeten.bp.temporal.TemporalAdjusters}.
For example, to find the first occurrence of a day-of-week after a given date, use
{@link org.threeten.bp.temporal.TemporalAdjusters#next(DayOfWeek)}, such as
{@code date.with(next(MONDAY))}.
</p>

<h4>Weeks</h4>
<p>
Different locales have different definitions of the week.
For example, in Europe the week typically starts on a Monday, while in the US it starts on a Sunday.
The {@link org.threeten.bp.temporal.WeekFields} class models this distinction.
</p>
<p>
The ISO calendar system defines an additional week-based division of years.
This defines a year based on whole Monday to Monday weeks.
This is modeled in {@link org.threeten.bp.temporal.IsoFields}.
</p>
</body>
